This study compared sitting time measured by a questionnaire (International Physical Activity Questionnaire; IPAQ) with concurrently measured objective sitting time from an accelerometer-based measure of thigh inclination (activPAL).Adults (n = 69), wore an activPAL for a week, and then completed the long-form 7 d recall IPAQ questionnaire. IPAQ reported sitting time (including and excluding transportation sitting) for the week, weekdays and weekend days were compared to activPAL (criterion measure) sitting time using intraclass correlation coefficients and Bland Altman plots.Confidence intervals between the IPAQ and the activPAL were wide, while correlations between the two measures were low and non-significant (0.112-0.275). Compared to a direct measure of postural sitting (activPAL), the IPAQ underestimated sitting time across the group for the whole week, both when including (mean 2.2 h d(-1)) and excluding (mean 3.4 h d(-1)) transportation sitting. Sitting was less accurately reported on weekend days than weekdays, and at lower levels of sitting on weekdays.Agreement between the IPAQ and the activPAL, a direct measure of sitting, in this study was poor. The direction of group agreement was different to comparisons using a measure of low accelerometer counts (Actigraph) as the criterion measure in previous research. Future studies should use a direct measure of sitting as a criterion measure to validate subjective measurement tools.